The present invention relates to a D/A conversion circuit, a data driver, an integrated circuit device, an electronic instrument, and the like.
As a liquid crystal panel (electro-optical device or display panel) used for electronic instruments such as portable telephones, a simple matrix liquid crystal panel and an active matrix liquid crystal panel that utilizes a switch element such as a thin film transistor have been known.
As disclosed in JP-A-2005-175811 and JP-A-2005-175812, a data driver (source driver) that drives data lines (source lines) of such a liquid crystal panel includes a D/A conversion circuit that outputs a grayscale voltage corresponding to grayscale data.
However, the circuit scale of the D/A conversion circuit increases as the number of bits of grayscale data increases due to an increase in the number of grayscales desired for a display panel.
An increase in display image quality has been desired for a liquid crystal panel. On the other hand, a reduction in power consumption and chip size has been desired for a data driver that drives a liquid crystal panel.
For example, JP-A-2005-175811 and JP-A-2005-175812 disclose a configuration that enables a Rail-to-Rail operation of an output circuit of a data driver that drives a data line while supplying a voltage to the data line with high accuracy.
According to the technologies disclosed in JP-A-2005-175811 and JP-A-2005-175812, the Rail-to-Rail operation is implemented by controlling the drive capability by providing an auxiliary circuit in each output circuit. Therefore, the circuit scale of the data driver increases due to the addition of the auxiliary circuit. Moreover, the transistor size must be increased in order to suppress a variation in voltage applied to the data line.
In order to supply an accurate voltage to the data line, a voltage output from a D/A conversion circuit that generates a grayscale voltage corresponding to grayscale data must be supplied directly to the data line. Therefore, it is necessary to increase the number of grayscale voltage lines as the number of grayscales increases, whereby the chip size increases.
An operational amplifier must be normally designed taking a variation in output voltage into consideration. Therefore, it is necessary to suppress a variation in output voltage by increasing the size of a transistor that forms an operational amplifier.